The present invention relates to a method for forming images using the imaging sheets described in U.S. Pat. No. 4,399,209. More particularly, it relates to a method for forming images on plain paper.
U.S. Pat. No. 4,399,209 to The Mead Corporation describes a transfer imaging system wherein an imaging sheet comprising a support and a layer of microcapsules containing a chromogenic material and a photosensitive composition is image-wise exposed to actinic radiation. The exposed sheet is next assembled with a developer sheet and the two are passed through a calender nip whereupon the microcapsules rupture and the contents of the microcapsules are image-wise transferred to the developer sheet where they react and form a colored image. Typically, the photosensitive composition is a photocurable composition containing an ethylenically unsaturated compound and a photoinitiator, the chromogenic material is a substantially colorless electron donating compound, and the developer is a electron acceptor such as an aromatic carboxylic acid salt.
Upon image-wise exposing the imaging sheet to actinic radiation, the internal phase of the microcapsules is hardened in the exposed areas. The internal phase in the unexposed areas remains liquid and the internal phase in areas receiving an intermediate level of exposure is hardened to an intermediate degree. Thus, the microcapsules in the unexposed areas are capable of rupturing and releasing the internal phase upon subjecting the exposed imaging sheet to a uniform rupturing force. The microcapsules in the underexposed areas may rupture and release the internal phase to an intermediate degree. In this manner, the internal phase of the microcapsules is image-wise transferred to the developer sheet where the image is obtained.
While the transfer imaging system described in U.S. Pat. No. 4,399,209 can be used in numerous formats and be designed to be useful in various applications, the user must purchase two coated paper products to reproduce images, namely, the imaging sheet and the developer sheet. It would be desirable to form images on plain paper. Furthermore, the final image is obtained on a chemically coated paper which may cause skin irritation and does not have a desirable feel.